Department of Earth Sciences, University of Manitoba, Winnipeg, MB, Canada R3T 2N2.
Environmental Molecular Sciences Laboratory (EMSL), Pacific Northwest National Laboratory, Richland, WA 99354, USA.
Environ Sci Process Impacts. 2022 Aug 17;24(8):1228-1242. doi: 10.1039/d2em00118g.
The large surface areas in porous organic matter (OM) and on the surface of altered minerals control the sequestration of metal(loid)s in contaminated soils and sediments. This study explores the sequestration of Cu by OM in surficial forest soil in close proximity to the Horne smelter, Rouyn-Noranda, Quebec, Canada. The organic-rich soils have elevated concentrations of Cu (Cu = 〈0.75〉 wt%) but lack associations between organic matter (OM) and Cu-sulfides, commonly observed in organic-rich Cu-contaminated soils. This provides a unique opportunity to study the sequestration of Cu by OM in a sulfur-depleted environment using a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atom probe tomography (APT). In two examined OM particles, Cu is predominantly sequestered as (I) nano- to micrometer-size Cu-bearing spinels, (II) as cuprite (CuO) nanoparticles or (III) finely dispersed Cu in association with clusters of magnetite (FeO) nanoparticles embedded in amorphous silica-rich pockets and (IV) in the OM matrix. The occurrence of euhedral crystals and nanoparticles in the single-digit range within the OM matrix indicate that the majority of the nanoparticles formed within the OM particles. A model is developed which proposes that the sequestration of Cu in OM is promoted by (I) the partial mineralization of the OM matrix by amorphous silica; (II) the nucleation of magnetite nanoparticles on highly reactive silanol groups; (III) the diffusion of Cu within mineralized and altered areas of the OM; (IV) the availability of Cu-bearing species, which in turn is controlled by the hydrodynamic properties of the pore channels; (V) the formation of precursors and nucleation of Cu-bearing nanoparticles. This study shows that the combination of SEM, TEM and APT provides new insights into the sequestration of metal contaminants by OM at various scales ranging from the single-digit nano- to micrometer scale.
多孔有机物（OM）的大表面积和变质矿物的表面控制着金属（类）在污染土壤和沉积物中的固定。本研究探讨了加拿大魁北克鲁恩-诺兰达霍恩冶炼厂附近地表森林土壤中 OM 对 Cu 的固定。富含有机物的土壤中 Cu 浓度升高（Cu = 〈0.75〉wt%），但缺乏有机富 Cu 污染土壤中常见的有机物质（OM）与 Cu-硫化物之间的关联。这为在硫贫环境中使用扫描电子显微镜（SEM）、透射电子显微镜（TEM）和原子探针断层扫描（APT）组合研究 OM 对 Cu 的固定提供了独特的机会。在两个检查的 OM 颗粒中，Cu 主要以（I）纳米至微米尺寸的含 Cu 尖晶石、（II）赤铜矿（CuO）纳米颗粒或（III）与嵌入非晶态富硅口袋中的磁铁矿（FeO）纳米颗粒簇相关的细小分散的 Cu 以及（IV）在 OM 基质中被固定。在 OM 基质中单个数字范围内的自形晶体和纳米颗粒的出现表明，大多数纳米颗粒是在 OM 颗粒内部形成的。提出了一个模型，该模型提出 OM 中 Cu 的固定是由以下几个因素促进的：（I）非晶态硅对 OM 基质的部分矿化；（II）磁铁矿纳米颗粒在高反应性硅醇基团上的成核；（III）Cu 在矿化和变质 OM 区域内的扩散；（IV）含 Cu 物种的可用性，而这又受孔隙通道水动力性质的控制；（V）Cu 载体制备物的形成和含 Cu 纳米颗粒的成核。本研究表明，SEM、TEM 和 APT 的组合为从单个纳米到微米尺度的各种尺度上 OM 对金属污染物的固定提供了新的见解。
